Ingredients Guide

What common supplement ingredients are, what they're used for, and how strong the evidence is. Each entry will link to a full page and to products that contain it.

Ingredient	Commonly used for	Evidence	Notes
Probiotics (Lactobacillus, Bifidobacterium)	Digestion, regularity	Moderate	Effects depend on the specific strain. Look for strain codes, not only species names.
Peppermint oil (enteric-coated)	Bloating, IBS symptoms	Moderate	May cause heartburn in some people.
Ginger	Nausea, digestion	Moderate	Best studied for nausea.
Inulin (prebiotic fiber)	Feeding gut bacteria, regularity	Limited	Can increase gas at first; start with a low dose.
S. salivarius K12 / M18	Bad breath, oral health	Limited	Small studies; promising but not conclusive.
Xylitol	Reducing cavity-causing bacteria	Limited	Toxic to dogs. Keep away from pets.
Collagen peptides	Skin elasticity, hydration	Limited	Many trials are small and industry-funded.
Biotin	Hair, nails	Insufficient	Helps only with true deficiency, which is rare. Can affect lab tests.
Omega-3 (fish oil) for pets	Skin, coat, joints	Moderate	Ask your vet for the right dose.

Ratings are our editorial summary of published research and will be updated as new studies appear. See Sources & Research.